Agatha Christie said this quote

“ I am pointing to you that under these conditions--mental strain, physical malaise--it is highly probable that dislikes that were before merely mild and disagreements that were trivial might suddenly assume a more serious note. The result of pretending to be a more amiable, a more forgiving, a more high-minded person than one really is, has sooner or later the effect of causing one to behave as a more disagreeable, a more ruthless and an altogether more unpleasant person than is actually the case! If you dam the stream of natural behavior, mon ami, sooner or later the dam bursts and cataclysm occurs. ”